Method for producing a crystallized aromatic polycarbonate, and

Details Method for producing a crystallized aromatic polycarbonate, and Method for producing a crystallized aromatic polycarbonate, and

1988-10-28

1990-08-14

Anderson, Harold D.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Treating polymer containing material or treating a solid...

528125, 528171, 528173, 528196, 528480, 528502, 528503, C08G 6440

Patent

active

049488716

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a method for producing a crystallized aromatic polycarbonate and a crystallized aromatic polycarbonate obtained thereby. More particularly, the present invention in concerned with an effective method for producing a crystallized aromatic polycarbonate, in which a prepolymer having a specific molecular weight and having a specific proportion of terminal aryl carbonate groups is prepared from a dihydroxydiaryl compound containing at least 85 mole % of a dihydroxydiaryl alkane, and a diaryl carbonate, and after crystallization thereof, the crystallized prepolymer is subjected to solid-state polymerization. Also, the present invention is concerned with a crystallized aromatic polycarbonate produced by the above-mentioned method which does not contain impurities, has a low terminal hydroxyl group content and is colorless and has further excellent properties, such as resistances to heat and to boiling water.
2. Background Art
In recent years, particularly in the last five or six years, aromatic polycarbonates have been widely employed in various fields as engineering plastics which have excellent heat resistance, impact resistance and transparency. Various studies have been made with respect to processes for producing aromatic polycarbonates. Up to now processes, such as one utilizing interfacial polycondensation of an aromatic dihydroxy compound, such as 2,2-bis(4-hydroxyphenyl)propane (hereinafter frequently referred to as "bisphenol A"), with phosgene (hereinafter frequently referred to as the "phosgene process"), have been commercially practiced. In the above-mentioned process, a mixed solvent of water or an aqueous alkali solution and a water-immiscible organic solvent is generally used. Commercially, a mixed solvent of an aqueous sodium hydroxide solution and methylene chloride is employed. As a catalyst for polymerization, a tertiary amine or a quaternary ammonium compound is employed. By-produced hydrogen chloride is removed as a salt with a base. The weight average molecular weight of the produced aromatic polycarbonate is generally about 23,000 to 70,000, normally 25,000 to 35,000.
However, in the interfacial polycondensation process employing phosgene, (1) phosgene (which is toxic) must be used, (2) due to the by-produced chlorine-containing compounds, such as hydrogen chloride and sodium chloride, the apparatus used is likely to be corroded, (3) it is difficult to remove impurities which adversely influence the polymer properties, such as sodium chloride from the polymer, and (4) since methylene chloride (which is generally used as a reaction solvent) is a good solvent for polycarbonate and has a strong affinity to polycarbonate, methylene chloride inevitably remains in produced polycarbonate. To remove the remaining methylene chloride on a commercial scale is extremely costly, and complete removal of the remaining methylene chloride from the obtained polycarbonate is almost impossible. Further, it is noted that the methylene chloride remaining in the polymer is likely to be decomposed, e.g., by heat at the time of molding, thereby forming hydrogen chloride, which not only causes corrosion of a molding machine but also lowers the quality of the polymer.
As mentioned above, the phosgene process involves too many problems to be practiced commercially.
Meanwhile, various methods are known in which an aromatic polycarbonate is produced from an aromatic dihydroxy compound and a diaryl carbonate. For example, a process, which is generally known as a transesterification process or a melt process, is commercially practiced. In the process, a polycarbonate is produced by performing a molten-state ester exchange reaction between bisphenol A and diphenyl carbonate in the presence of a catalyst, while effecting elimination of phenol. However, in order to attain the desired polymerization degree of the final aromatic polycarbonate according to this process, phenol and, finally, diphenyl carbonate need to be distilled off from a formed molten polycar

REFERENCES:
patent: 3888826 (1975-06-01), Yamana
patent: 4107143 (1978-08-01), Inata

Affiliated with

Also associated with

Rating

Method for producing a crystallized aromatic polycarbonate, and does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method for producing a crystallized aromatic polycarbonate, and , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing a crystallized aromatic polycarbonate, and will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-463790